How we measure your chargeable area

The size of your chargeable area determines how much you pay for your surface water drainage and highway drainage services.

To determine your chargeable area, we measure the total site area of your premises (whether or not the surface area is permeable) including the boundary and all land held within the boundary, and then exclude any permanently grassed, cultivated or landscaped areas, where no surface water or ground water drains into a public sewer. 

The diagram below shows how we calculate your chargeable area, and how we use this measurement to allocate a site area charging band for your premises.

Site area charge band calculation

To see how your site is mapped, please use our site area map checking service.

Points to note:

Any area that has a surface water connection to a public sewer, even if it is permanently grassed, cultivated or landscaped will still be chargeable and included in the measurement of the chargeable area.  Public highways are excluded from our measurements where they fall within the site boundaries.